We are calling to 'confirm your appointment' with Dr. Jones. = We are calling to make sure that you will 'keep your appointment' with Dr. Jones.
The museum is open to visitors 'by appointment' only. [=you have to make an appointment to visit the museum]
The court ordered the 'appointment' of an attorney to represent the child.
(..) would you? No. Excuse me. Are you Miss Halliwell? Prue Halliwell? Yes. Did we have an appointment? No. Actually, I'm looking for someone, and I believe you can help me. I find objects, not people. Well, I think you might know her. I saw you talking to her earlier. (..)1998 TvShow: Charmed Title: The Truth Is Out There... and It Hurts Season: 1 Episode 8